PROJECT SUMMARY/ABSTRACT Breastfeeding in the US has radically changed over the past two decades: feeding at the breast was once the norm, but now more than 85% of infants fed human milk are fed expressed milk from a bottle at least some of the time, and 5-7% of human-milk fed infants are never fed at the breast at all. Data from national surveys are routinely used to inform and evaluate breastfeeding promotion efforts at the national and local levels and are also the basis for research, but the questions currently in use in NCHS surveys no longer reflect contemporary infant feeding and lactation practices and result in significant measurement error. Our long-term goal is to contribute a new understanding of the impact of contemporary infant feeding and lactation practices on maternal and child health. Our objective here, which is the next step towards that goal, is to develop and evaluate a brief set of survey questions to accurately capture these practices among respondents. We will meet this objective by building on our prospective Moms2Moms study to survey mothers of children aged 0-5 years. Our objective was formulated based on our preliminary data revealing that up to 19% of children in our Moms2Moms study would have been misclassified as ?not breastfed? or had human milk feeding duration values that were under/overestimates of greater than 1 month if the NCHS questions had been used rather than our pilot survey questions. The rationale for the proposed project is to support future, high-quality research and public health surveillance of maternal and child health which use federal survey data. We plan to attain our objective by pursuing the following Specific Aims: 1) Develop and evaluate a concise set of survey questions about lactation and infant feeding that reflect contemporary practices, and 2) Ensure any recall bias imposed by our question set is equivalent to or less than the bias imposed by the questions currently used in NCHS surveys. The approach will include 3 phases: Pretest, Cross-sectional Field Test, and Comparison with Prospective Data. The proposed research is innovative because it will proactively address pitfalls by systematically pre-testing our question set before fielding with respondents, it will formally test our question set against the existing NCHS questions for direct comparison, and it will directly estimate recall bias by comparing responses to our question set to prospective data collected with the same respondents 4 years' previous. Through the research proposed in this application, we expect to contribute a new, concise, field-tested set of questions that may be used in NCHS surveys and also non-federal surveys. This contribution is significant because it will have a direct, positive impact on the quality of the data produced by these surveys, and thereby, a positive impact on the quality of research and surveillance efforts that rely on these data.